In an effort to increase the performance and speed of semiconductor devices, semiconductor device manufacturers have sought to reduce the linewidth and spacing of interconnects while minimizing the transmission losses and capacitative coupling of the interconnects. One way to diminish power consumption and capacitative coupling is by decreasing the dielectric constant (also referred to as “k”) of the insulating material, or dielectric, that separates the interconnects. Insulator materials having low dielectric constants are especially desirable, because they typically allow faster signal propagation, reduce capacitive effects and cross talk between conductor lines, and lower voltages required to drive integrated circuits.
Since air has a dielectric constant of 1.0, a major goal is to reduce the dielectric constant of insulator materials down to a theoretical limit of 1.0, and several methods are known in the art for reducing the dielectric constant of insulating materials. These techniques include adding elements such as fluorine to the composition to reduce the dielectric constant of the bulk material. Other methods to reduce k include use of alternative dielectric material matrices.
Therefore, as interconnect linewidths decrease, concomitant decreases in the dielectric constant of the insulating material are required to achieve the improved performance and speed desired of future semiconductor devices. For example, devices having interconnect linewidths of 0.13 or 0.10 micron and below seek an insulating material having a dielectric constant (k)<3.
Currently silicon dioxide (SiO2) and modified versions of SiO2, such as fluorinated silicon dioxide or fluorinated silicon glass (hereinafter FSG) are used. These oxides, which have a dielectric constant ranging from about 3.5–4.0, are commonly used as the dielectric in semiconductor devices. While SiO2 and FSG have the mechanical and thermal stability needed to withstand the thermal cycling and processing steps of semiconductor device manufacturing, materials having a lower dielectric constant are desired in the industry.
Methods used to deposit dielectric materials maybe divided into two categories: spin-on deposition (hereinafter SOD) and chemical vapor deposition (hereinafter CVD). Several efforts to develop lower dielectric constant materials include altering the chemical composition (organic, inorganic, blend of organic/inorganic) or changing the dielectric matrix (porous, non-porous). Table I summarizes the development of several materials having dielectric constants ranging from 2.0 to 3.5. (PE=plasma enhanced; HDP=high-density plasma) However, these dielectric materials and matrices disclosed in the literature, patent applications or patents shown in Table 1 fail to exhibit many of the combined physical and chemical properties desirable and even necessary for efficient dielectric materials, such as mechanical stability, thermal stability, high glass transition temperature, or appropriate hardness, while at the same time still being able to be solvated and spun on to a substrate, wafer or other surface. Therefore, it may be useful to investigate other compounds and materials that may be useful as dielectric materials and layers, even though these compounds or materials may not be currently contemplated as dielectric materials in their present form.
TABLE IDEPOSITIONMATERIALMETHODKREFERENCEFluorinatedPE-CVD;3.3–3.5U.S. Pat. No. 6,278,174siliconHDP-CVDoxide (SiOF)HydrogenSOD2.0–2.5U.S. Pat. Nos.Silsesquioxane4,756,977;(hereinafter5,370,903; andHSQ)5,486,564;International PatentPublicationWO 00/40637;E. S. Moyer et al.,“Ultra Low kSilsesquioxane BasedResins”, Concepts andNeeds for Low DielectricConstant <0.15 μmInterconnect Materials:Now and the NextMillennium,Sponsored bythe American ChemicalSociety, pages 128–146(Nov. 14–17, 1999)MethylSOD2.4–2.7U.S. Pat. No. 6,143,855Silsesquioxane(hereinafterMSQ)PolyorganosiliconSOD2.5–2.6U.S. Pat. No. 6,225,238FluorinatedHDP-CVD2.3U.S. Pat. No. 5,900,290AmorphousCarbon (a-C:F)BenzocyclobuteneSOD2.4–2.7U.S. Pat. No. 5,225,586(hereinafter BCB)Polyarylene EtherSOD2.4U.S. Pat. Nos.(hereinafter PAE)5,986,045,5,874,516, and 5,658,994Parylene (N and F)CVD2.4U.S. Pat. No. 5,268,202(AF4)PolyphenylenesSOD2.6U.S. Pat. Nos. 5,965,679and 6,288,188B1; andWaeterloos et al.,“Integration Feasibilityof Porous SiLKSemiconductorDielectric”. Proc. Of the2001 InternationalInterconnect Tech. Conf.,pp. 253–254 (2001).
Reichert and Mathias describe compounds and monomers that comprise adamantane molecules, which are in the class of cage-based molecules and are taught to be useful as diamond substitutes. (Polym, Prepr. (Am. Chem. Soc., Div. Polym. Chem.), 1993, Vol. 34(1), pp. 495–6; Polym, Prepr. (Am. Chem. Soc., Div. Polym. Chem.), 1992, Vol. 33 (2), pp. 144–5; Chem. Mater., 1993, Vol. 5 (1), pp. 4–5; Macromolecules, 1994, Vol. 27 (24), pp. 7030–7034; Macromolecules, 1994, Vol. 27 (24), pp. 7015–7023; Polym, Prepr. (Am. Chem. Soc., Div. Polym. Chem.), 1995, Vol. 36 (1), pp. 741–742; 205th ACS National Meeting, Conference Program, 1993, pp. 312; Macromolecules, 1994, Vol. 27 (24), pp. 7024–9; Macromolecules, 1992, Vol. 25 (9), pp. 2294–306; Macromolecules, 1991, Vol. 24 (18), pp. 5232–3; Veronica R. Reichert, PhD Dissertation, 1994, Vol. 55–06B; ACS Symp. Ser.: Step-Growth Polymers for High-Performance Materials, 1996, Vol. 624, pp. 197–207; Macromolecules, 2000, Vol. 33 (10), pp. 3855–3859; Polym, Prepr. (Am. Chem. Soc., Div. Polym. Chem.), 1999, Vol. 40 (2), pp. 620–621; Polym, Prepr. (Am. Chem. Soc., Div. Polym. Chem.), 1999, Vol. 40 (2), pp. 577–78; Macromolecules, 1997, Vol. 30 (19), pp. 5970–5975; J. Polym. Sci, Part A: Polymer Chemistry, 1997, Vol. 35 (9), pp. 1743–1751; Polym, Prepr. (Am. Chem. Soc., Div. Polym. Chem.), 1996, Vol. 37 (2), pp. 243–244; Polym, Prepr. (Am. Chem. Soc., Div. Polym. Chem.), 1996, Vol. 37 (1), pp. 551–552; J. Polym. Sci., Part A: Polymer Chemistry, 1996, Vol. 34 (3), pp. 397–402; Polym, Prepr. (Am. Chem. Soc., Div. Polym. Chem.), 1995, Vol. 36 (2), pp. 140–141; Polym, Prepr. (Am. Chem. Soc., Div. Polym. Chem.), 1992, Vol. 33 (2), pp. 146–147; J. Appl. Polym. Sci., 1998, Vol. 68 (3), pp. 475–482). The adamantane-based compounds and monomers described by Reichert and Mathias are preferably used to form polymers with adamantane molecules at the core of a thermoset. The compounds disclosed by Reichert and Mathias in their studies, however, comprise only one isomer of the adamantane-based compound by design choice. Structure A shows this symmetrical para isomer 1,3,5,7-tetrakis(4-phenylethynylphenyl)adamantane:

In other words, Reichert and Mathias in their individual and joint work contemplate a useful polymer comprising only one isomer form of the target adamantane-based monomer. A significant problem exists, however, when forming polymers with the single isomer form (symmetrical “all-para” isomer) 1,3,5,7-tetrakis[(4′-phenylethynyl)phenyl]adamantane of the adamantane-based monomer. According to the Reichert dissertation (supra) and Macromolecules, vol. 27, (pp. 7015–7034) (supra), the symmetrical all-para isomer 1,3,5,7-tetrakis[(4′-phenylethynyl)phenyl]adamantane “was found to be soluble enough in chloroform that a 1H NMR spectrum could be obtained. However, acquisition times were found to be impractical for obtaining a solution 13C NMR spectrum.” Thus, the Reichert symmetrical “all-para” isomer 1,3,5,7-tetrakis[(4′-phenylethynyl)phenyl]adamantane would not be useful in any application requiring solubility or solvent-based processing, such as flow coating, spin coating, or dip coating.
Although various methods are known in the art to lower the dielectric constant of a material, all, or almost all of them have disadvantages. Thus, there is still a need in the semiconductor industry to a) provide improved compositions and methods to lower the dielectric constant of dielectric layers; b) provide dielectric materials with improved mechanical properties, such as thermal stability, glass transition temperature (Tg) and hardness; and c) produce thermosetting compounds and dielectric materials that are capable of being solvated and spun-on to a wafer or layered material.